Printful has premium luster and premium matte prints available that SixthLeafClover and I have certified to be of same quality as what we make in-house. You pay them for the listed production cost but you set your own selling price. Plus, they have fulfillment partners throughout the world so they can ship your prints to your customers abroad at their domestic postage rates. The only drawback is no NSFW as their fulfillment partners might not appreciate porn.

I'd avoid Displate as there are some controversies involving Displate and copyright holders. Also, Displate is currently overrun by generative AI junks and your stuff might end up getting scraped by bots to be listed back on Displate under other sellers for cheaper. Getting Displate to respond to DMCA takedowns is like getting United Healthcare to approve a claim for a major surgery.

If you're having trouble with infringement, I came across this the other day: https://www.justice4artists.com/. Can't vouch for it but it would be big if true.

Some artists have used this service to recover money. But also, it would be a measure to burn bridges as those platforms would absolutely never ever do business with those who went into litigation against them. So this is a measure of "I have zero interest working with this platform in my lifetime and I don't like the fact that they allow their users to use my art without my permission and therefore I have no qualm about light them up with aggressive litigations." Other than that issue, the service is legitimate as it actually goes through legal process to obtain entitled damage compensations for you. They take a good chunk of the money as their contingency fees and you get the money that you otherwise would never get yourself.

I recently learned about a site called Fourthwall, https://fourthwall.com/, that looks interesting. I've never used this site, so this isn't a recommendation. But it might be worth looking into. I suppose there is also Society 6 as an alternative, but you might run into the same issues. I honestly, gave up on print on demand sites a while ago, as I couldn't get my art to print very well half the time. I was never quite satisfied with the quality (I think this had more to do with my art style than any mistake on their part). But I might try again at some point. Anyway, good luck on your search!

I just want to add that Society6's mechandise quality has gone down hill a lot lately and last time we worked with them there were troubling signs of internal struggles and turmoil that felt like the company is imploding rapidly. Society6's old faithful are now swinging to Printful.